Wet to dry self-transitions in dense emulsions: from order to disorder and back

TL;DR

This paper investigates how dense emulsions can spontaneously transition between ordered and disordered states in microfluidic channels, revealing nonlinear dynamics driven by device geometry and unexpected reordering phenomena.

Contribution

It demonstrates the self-transitions between order and disorder in dense emulsions within microfluidic channels, highlighting the role of geometry and nonlinear forces in these processes.

Findings

Transitions between ordered and disordered emulsions are driven by channel geometry.

An unexpected reordering occurs at large aperture angles.

The competition between viscous forces and surface tension governs the transitions.

Abstract

One of the most distinctive hallmarks of many-body systems far from equilibrium is the spontaneous emergence of order under conditions where disorder would be plausibly expected. Here, we report on the self-transition between ordered and disordered emulsions in divergent microfluidic channels, i.e. from monodisperse assemblies to heterogeneous polydisperse foam-like structures, and back again to ordered ones. The transition is driven by the nonlinear competition between viscous dissipation and surface tension forces as controlled by the device geometry, particularly the aperture angle of the divergent microfluidic channel. An unexpected route back to order is observed in the regime of large opening angles, where a trend towards increasing disorder would be intuitively expected.